Some Useful Websites:

WoodforTrees.org for your temperature graphing needs of the last century:
http://www.woodfortrees.org/plot/gistemp/mean:36 (here with a 3 year moving average of GISTEMP)

The NOAA Climate Indicators site:
http://www.ncdc.noaa.gov/bams-state-of-the-climate/2009-time-series/arctic_seaice (here showing September sea ice)

Satellite-measured sea level:
http://sealevel.colorado.edu/

More Arctic:
http://nsidc.org/arcticseaicenews/
http://arctic.atmos.uiuc.edu/cryosphere/
http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm

The Charney Report (first major climate assessment to start making definitive statements... in 1979)
http://www.atmos.ucla.edu/~brianpm/charneyreport.html

I may add more later,

-Marcus